Simulation of the local structure, properties of mixing, and stability of solid solutions Ba$_{x}$Sr$_{1-x}$CO$_{3}$ by the interatomic potential method

The strontianite (SrCO$_3$)–witherite (BaCO$_3$) solid solutions have been simulated using the interatomic potential method. The dependences of the unit cell parameters, the unit cell volume, and the bulk modulus on the composition of the solid solution have been constructed. It has been shown that the unit cell volume and the bulk modulus exhibit negative deviations from the additivity. An analysis of the local structure of the solid solutions has been carried out. It has been found that, for the equimolar composition of the Ba$_{x}$Sr$_{1-x}$CO$_{3}$ solid solution, the relaxations of the barium and strontium positions are equal to 60 and 56%, respectively. It has been established that the enthalpy of mixing is positive and, for the equimolar composition of the solid solution, reaches a maximum value of 3.4 kJ/mol. The obtained results have been compared with the experimental data. The solvus of the Ba$_{x}$Sr$_{1-x}$CO$_{3}$ system has been constructed based on the dependences of the Gibbs free energy on the composition in the temperature range from 300 to 1000 K.